The present invention relates to a photolytic polymer and a photoresist composition, and more particularly to a photolytic polymer having a sulfonium salt unit in its main chain.
Recently, studies and developments of chemically amplified resists as high sensitivity of resists have been productive. Such chemically amplified resists show a generation of acid through an exposure from a photo acid generator in the photoresist. Further, the generated acid causes a catalytic reaction. This results in a rapid improvement in a sensitivity of the photoresist. It is thus important to select a suitable photo acid generator for the chemically amplified resist. It is required to produce a photo acid generator having much higher sensitivity. In the past, various types of the photo acid generators have been synthesized. An example of low molecular photo acid generators is a low molecular triphenylsulfonium salt disclosed in Crivello et al., Journal of the Organic Chemistry, 1987, Vol. 43, pp. 3055-3058. One example of high molecular photo acid generators is, for example, a high molecular derivative having a sulfonium salt unit in its side chain, which is disclosed in Yamada et al., Makromolekulare Chemie, 1972, Vol. 152, 153. Another is a high molecular derivative having a sulfonium salt unit in its main chain, which is disclosed in Crivello et al., Journal of Polymer Science Polymer Chemistry, 1987, Vol. 25, p. 3293.
Up-to-date technologies for improvement in high density and high integration of semiconductor devices, however, require compositions having much higher photo-sensitivity. Namely, it has been required to develop a sensitive material which has a high efficiency of the photo-sensitivity and/or an ability to change a solubility of the photoresist much more remarkably. The conventional compositions are too insufficient to respond to the above requirements by the up-to-date technologies. It has been required to develop a much more useful photolytic polymer and photo acid generating polymer.